The material predominantly used for making recorders is wood, but ivory, plastics and metal are also used. All recorders made from these materials suffer from the common disadvantage of high susceptibility to condensation in the blowing duct of humidity from the breath. This breath humidity accumulates as large of small droplets on the walls of the blowing duct. This leads to a disturbance to the air passing through this blowing duct, resulting in the recorder becoming "husky." The forming of moisture deposits is to be expected after playing for some time. However when the atmosphere is cold or when the breath is especially humid, disturbing degree of precipitation may also occur after only a short period of play. Although wood is a material which to a certain extent, absorbs moisture, this property is not sufficient to prevent humidity-dependent effects upon the quality of the musical tone after a long period of play.
In the case of wooden recorders which are the predominant type, the effect of humidity in the blowing duct of the recorder is to have not only an instantaneous deleterious effect upon the play but also in the longer term it prevents a consistent and constant quality of tone. The walls of the blowing duct gradually lose their smooth surface by the continual influence of moisture. Fibrous and roughened regions are produced more or less rapidly, which modify the flow of air in the blowing duct. In addition, the continuous, intense influences of humidity during play, and the consequent drying out during intervals between play, lead to swelling and shrinking of the wood, which can modify the internal dimensions of the blowing duct in a manner adverse to the guidance of the wind through it. Since changes in dimensions of the order of only 0.02 mm lead to a detectable change in tone, recorders equipped in this manner lose the quality of their tone over a period of time.
Various different measures have already been proposed to counteract these wear phenomena in the blowing duct of wooden recorders. Thus it is known that the blowing duct may be fitted with a lining of a moisture-repellent material, intended for preventing the moisture from penetrating into the wood and producing the effects described. An increased resistance to wear in the blowing duct is indeed achieved by this measure, but the precipitation and retention of the breath humidity in the form of small droplets in the blowing duct is not prevented. Since the precipitating droplets remain completely on the surface of the lining and even the slight water absorption of the wood is suppressed, the capability for play of the instrument is in no way improved.
Another known and, by comparison, much better measure consists in the covering of the blowing duct, at least on two wall faces, with finely porous, ceramic, absorbent platelets. These platelets are glued to surfaces in the blowing duct and are capable of absorbing the condensing droplets so that the latter disappear from the surface of the blowing duct walls. In the long term however this measure, in itself good, does not prove to be entirely satisfactory. One reason is that the platelets, which, by their very nature cannot possess a large volume, rapidly become completely saturated with moisture. Another reason is that hitherto there is no adhesive which will satisfy the requirements imposed. As soon as the platelets have become saturated, they can no longer absorb any further humidity. It follows that from this instant onwards an adverse effect upon the playing capability of the recorder again occurs. In addition, the adhesive now becomes humid and like the wood beneath it commences to swell so that the inserted platelets become displaced. It has been found that in the course of time, the platelets, become partly loosened from their supporting surfaces in the blowing duct. In any case, the required dimensional accuracy of the blowing duct is lost as a result of this effect.
It is an object of the invention to overcome these disadvantages of the known recorders having an absorbent wall to the blowing duct.